An electromagnetic ally operated fuel injector is described in German Published Patent Application No. 38 08 635, which describes a valve closing section designed on an axially movable valve needle to work together with a fixed valve seat for opening and closing the valve. The valve closing section is designed with a conical shape narrowing in the downstream direction, while the valve seat has the form of a truncated cone. This valve closing section forms the downstream end of the valve needle which tapers to a conical tip. Upstream from the valve closing section and the valve seat, the valve needle is provided with a plurality of spiral-shaped fuel channels through which fuel to be injected reaches the valve seat with a swirl to improve fuel atomization and control the fuel flow rate.
In addition to the conically tapered downstream tip of the valve needle, U.S. Pat. No. 5,350,119 describes a fuel injector having an axially movable valve needle with a rounded valve closing section forming the downstream end of the valve needle.
In addition, German Patent No. 30,46 889 describes a fuel injector having a flat armature and a valve closing part attached thereto. This movable valve member works together with a valve seat rigidly connected to the housing. The closing part has a convex valve closing section sealed by a flat polished section running perpendicular to the longitudinal axis of the valve. Downstream from the valve seat is a collecting space whose volume should be as small as possible and which is delimited by the valve seat body, the flat lower end of the valve closing section and the opposite planar upper bordering face of a swirl body arranged downstream from the valve seat body. Each swirl body has a plurality of swirl channels beginning at the side of the swirl body and opening into a central swirl chamber.
Japanese Laid Open Patent Application No. 10047210 describes a fuel injector for a fuel injection system of an internal combustion engine, where the fuel injector has an energizable actuating element and a valve needle that is movable axially along a longitudinal axis of the valve and has on its downstream end a valve closing section which works together with a fixed valve seat to open and close the valve. The valve seat is designed on a flat valve seat element. Upstream from the valve seat, the valve has a swirl body which functions as a guide for the valve needle and also produces a swirl in the fuel spray. Downstream from the valve seat, a flattened face running perpendicular to the longitudinal axis of the valve is provided on the downstream end of the valve closing section. The valve seat is followed by an outlet orifice having a diameter D which is much greater than the diameter of the flattened face formed on the valve needle.